the '98 engines
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Changes in US engines point the way for European technology. In the first part of a series on engine development in the US we look at Mack; over coming weeks we'll be analysing the new engines from Cummins, Caterpillar, Detroit Diesel and Navistar.
Heavy-duty diesels are set to change in North America again in 1998. The next round of US emissions reguladons bites at the beginning of the year—and what America does today, Europe is likely to be doing tomorrow. The goalposts are only moving a little, but engine development has reached the stage of diminishing returns
where major investments in design time and resources have to be made for even small gains in exhaust emissions.
As tighter and tighter emission controls are introduced, electronic controls will spread downwards from the heavy end of the market through middleweight diesels and into lighter CVs. With the electronics come many of the features we've come to expect on the big engines: drive-by-wire, PTO control, cruise control, speed limiting, gear-down protection, fuel consumption gains, idling information... the list gets longer with each generation of electronics controls.
This migration down the weight range brings with it clean-burning engines that meet US 1998 levels without recourse to expensive catalytic converters and trouble-prone soot traps. It also answers the needs of fleets running mixed middle and heavyweight trucks and using computers to track, dispatch, manage and maintain their vehicles.
The clean-running engines due to be launched next year reflect an interesting trend: electronics are not only becoming common across different families within a manufacturer's product range; systems from the likes of Motorola, Bosch and Diesel Technology are becoming standard across the industry.
In the US this is equally good news for the single truck operator and the mixed fleet as common electronic diagnostic and repair tools are bound to bring down prices.
Mack has opted for electronic controls and unit-pump technology on its 12-litre E7 diesel to meet US 1998 emissions levels. As the E7 made its European debut in the Renault Magnum last year, these changes are likely to make their way across the Atlantic.
The latest E-Tech engine specifications include an upgrade to V-MAC III, Mack's electronic engine control. This will provide additional fuel-system controls and electronic features for Mack engines and chassis through to the tough US 2004 emissions hurdle and beyond.
"The E7 Unit Pump is more than a product," says Mack's Steve Homcha. "It is part of the (Mack/Renault) global strategy to meet environmental demands in 1998 without sacrifices on the part of the customer. It is our building block to the 21st Century."
As well as the revamped E7, Mack's 1998 engine line-up will include updated versions of the 16.4-litre E9 vee-eight engine which is also used in the Renault Magnum. Electronic V. MAC E9 engines could offer European operators up to 610hp (455kW).
For North America, the 10-litre E5, based on the Renault (RVI) 10-litre diesel, made its debut at the recent Mid-America Trucking Show (CM 3-9 April).
New concept
The electronic unit pump (EUP) is a relatively new concept that made its debut in North America on the Detroit Diesel 12-litre Series 55 engine which is currently exclusive to Freightliner. Mercedes uses the same principle on its new 500 Series engines; other European producers are likely to follow suit.
Like the Series 55, the Mack E-Tech EUP uses a dedicated pump for each cylinder, mounted to the side of the cylinder block next to the camshaft. Each pump is driven from its own cam lobe, and each has a 430mm line between pump and nozzle to maintain exact injection timing.
The pumps' fuel delivery is controlled electronically at the pump, with V-MAC III dictating the amount of fuel delivered and the injection timing via solenoid valves on the pumps. This unit-pump technology is a halfway-house between a typical pump-linenozzle (PIN) system using an in-line pump and an electronic unit-injector system that uses the same sort of electronic controls but at the injector in the head.
The benefit of the EUP concept is that it can be applied to an existing engine without a complete redesign.
The Mack E7 block has been changed to accommodate a much larger camshaft, built to withstand the high injection pressures generated by the unit pumps (now up to 26,000psi from 17.000psi in the Mack PLN engines). This has doubled the weight of the old shaft and added a third lobe. The camshaft drive has also been beefed up to withstand the torsional vibrations.
Engine block
The engine block has also been modified to provide a deck for mounting the pumps. At the same time Mack strengthened the block to cope with higher cylinder pressures. The top end is basically unchanged, however, as the simple injector can easily be accommodated in the four-valve heads.
Most of the injection system is external to the engine, so each pump, line and nozzle can be easily serviced. The final installation has a deflector plate over the top of the pumps, partly-to contain their mechanical noise.
Individual circuits for each cylinder improves the electronic diagnostics, allowing individual cylinder performance to be checked, and timing adjustment is no longer necessary.
Another service change is the need for more effective fuel filters to protect the unit pump. Higher pressures demand closer running tolerances within the pumps, so clean fuel is essential. To stop old filters being fitted to the new systems the spin-on filters have a different thread size.
More fuel is returned to the tanks with the unit pumps but as the controls are mounted down on the pumps this return fuel does not pick up additional heat from the cylinder head.
The injectors are made for Mack by Bosch; the unit pumps are by Diesel Technology, which also supplies the Series 55 pumps.
The E-Tech technology is said to improve the engine's driveability, performance and economy. Mack says this results from the mechanical advantages introduced in the EUP concept combined with the latest V-MAC III electronic controls.
Even with no change to the combustion chamber or the high-swirl induction/head, Mack claims that the EUP engines use 10-15% less fuel than mechanically governed PLN engines, and 2-3% better than the electronic VMAC II PLN engines.The throttle response of the engines is said to be faster too.
Eliminating the in-line pump for the unit pumps has changed the engine's noise characteristics. Overall noise levels are unchanged but Mack is looking for ways to make a significant improvement here too.
At present 4,000 engines a year are crossing the Atlantic to power high-horsepower RVI models. As this increases to a target of 20,000 a year, further noise reductions will help meet tough European drive-by noise restrictions.
Exhaust brakes and retarders are essential in Europe, so Mack has introduced a new-technology Jacobs Brake which offers up to 360hp (268kW) of retardation.
While the launch of the new fuel system presents a good opportunity to overhaul V-MAC, further improvements to the vehicle manage
ment and control system are already on the way. V-MAC IV could be ready within three years and the fifth generation is already at the concept stage.
According to Mack, the change to EUP has dictated major hardware as well as software changes. The fuel-control solenoids on the pumps dictate high current power handling, so for the first time for Mack has included an on-engine electronic module. This has allowed a 30% reduction in the number of wires running through the firewall to the second electronic control unit.
The architecture chosen by Mack is essentially an open standard. In exchanging engines across the MacldRV1 partnership, the corporation faces many of the same concerns that truck builders/assemblers already experience in the US.
The third-generation system released with ELT has J1587 and J1939 serial communications, a fast processor and more memory. The system is designed by Mack with a Bosch onengine controller and electronic control unit (ECU). The vehicle ECU is made by VDO and includes additional vehicle management functions including a trip recorder.
Different ratings
A number of different ratings will be available with the EU' engines. At the top of the range the 460, develops 1001bft (135Nm) more torque than the 454 that it replaces. The 427hp (318kW) version is retained with its 1,5601bft (2,115 Nm) of torque.
The E7 is by no means at the end of its development: future models are likely to top the 500hp mark.
Mack is now busy developing electronics for the E5 Renault-derived 10-litre diesels which could soon make their way across to Europe. Within a few years, they will gain four-valve heads and more power ratings to enhance their appeal and overlap with the bottom end of the E7 range.
By the end of this decade, Mack expects to be offering a wide, well integrated engine range across its US and European product lines as emissions regulations come together on both sides of the Atlantic.
by Steve Sturgess.